This invention relates to the emergency shutoff of a section of pipeline and more particularly to a pincer mechanism which may be used to squeeze off small diameter plastic or steel pipe on one or both sides of a break or leak.
Those skilled in the art are aware of the problem of time involved in shutting down a section of pipeline that has developed a break or leak. In the case of gas, a leak in the line is always potentially dangerous and therefore, it is important if not critical that the break be isolated and shut off at the earliest possible moment. One current practice is to close the nearest valves in the system on either side of the break in the line. Since valves in the line may be some distance apart, depending upon such factors as population density and nature of the area served, a substantial amount of damage may be done before the valves can be closed. Also, shutting the valves may involve interruption of service to a number of customers if the section controlled by the valves is large. One practice for stopping leaks is to attach fittings on both sides of the break in order to stop flow to the point of the break. Installation of fittings requires time and may be dangerous for the workmen. In any event, a hole or trench must be dug to expose the break in the line. Utilities such as gas companies are criticized for the length of time required to close off leaks and frequently are also criticized for the size of the section of pipe distribution line which is shut down. If the fluid excaping from the pipe is liquid the tendency for the liquid to wash away supporting soil and undermine pipe support may increase the danger to workmen as well as the public.
While manually operated pipe pincer units have been offered in the marketplace for some time, nevertheless none are known which are specifically designed to do a combination of jobs, that is to service both small diameter steel and plastic lines and also to be used as a booming-on tool when steel pipe is being patch welded.